I recently served as a "private sector representative" in a panel discussion before an audience of foreign graduate students at the University of Tokyo. Many of the students will soon be seeking employment in Japan; because I have spent 25 years living in or traveling to Japan, the last 10 or so running my own small, Japan-focused business, I was asked to speak about networking and building a reputation in Japan.
"Networking" brings to mind often-contrived group events, name tags and awkward attempts at conversation with strangers. These kind of formal networking events do take place in Japan but are generally not a very effective method for building professional relationships here, at least with Japanese people.
Networking (even the word sounds coldly clinical) with Japanese people should not be impersonal or mercenary, and instant gratification (in terms of gaining business or employment) should ordinarily not be expected or sought. The objective should be building long-term trusting, reciprocal relationships; business or other opportunities might eventually flow from such a relationship, but the relationship is an end in itself, not merely a means to an end.